1. Technical Field
The present invention relates to a harm-removing agent and a method for rendering halogen-containing gas harmless, which can render harmless the exhaust gas containing halogen-containing gas discharged from a dry etching or cleaning step in a manufacturing process of a semiconductor device, and also relates to a method for manufacturing a semiconductor device using them.
2. Background Art
At the dry etching in the manufacturing process of a semiconductor device, a material subjected to the etching, such as SiO2, Si, SiW, SiN, Al, GaAs, GaP and InP, is etched using, for example, one or more gas selected from fluorocarbon-type gas, sulfur hexafluoride, hydrogen halide (e.g., hydrogen chloride), boron trichloride and halogen gas (e.g., chlorine gas), and according to the purpose, one or more gas selected from oxygen, nitrogen, hydrogen, argon and helium is added to the etching gas. The exhaust gas discharged from the etching apparatus contains gases produced during the etching in addition to the etching gas, such as silicon halide, tungsten halide, carbonyl halide, sulfur tetrafluoride and sulfur dioxide.
As the means for rendering harmless the exhaust gas containing such halogen-containing gas discharged from the manufacturing process of a semiconductor device, a wet process and a dry process are heretofore known. The wet process requires complicated equipment and has a problem in the after-treatment of the absorbing solution or in the operability. Furthermore, since the exhaust gas is washed with an aqueous solution of alkali such as sodium hydroxide or sodium carbonate, the halogen-containing gas may react with the alkali aqueous solution depending on the case to produce solid matters and therefore the gas outlet line of the treating apparatus may be clogged. Because of these problems, the wet process is not applied widely.
On the other hand, the dry process is expected to have capability of easily improving the problems of the wet process and a large number of agents and methods for removing harmful gas have been proposed.
Examples of the methods include:
(1) a method of using a harm-removing agent obtained by attaching triiron tetroxide to the surface of soda lime (see, JP-A-6-2213 (the xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d)),
(2) a method of contacting the gas with activated carbon and then with iron oxide (see, JP-A-6-319947),
(3) a harm-removing agent mainly comprising iron oxide and a manganese compound and a method of contacting the gas with the harm-removing agent, and then contacting the gas with activated carbon having supported thereon a metal oxide (see, JP-A-6-198128),
(4) a method of using a harm-removing agent mainly comprising strontium hydroxide and a harm-removing agent containing water moreover (see, JP-A-7-275645),
(5) a method of using a harm-removing agent mainly comprising triiron tetroxide and a harm-removing agent containing water moreover (see, JP-A-7-275646), and
(6) a method of using a harm-removing agent comprising activated carbon having supported thereon an aluminate of alkali metal or tetraalkylammonium (see, JP-A-4-210236).
In any of these methods, the dry etching exhaust gas containing halogen-containing gas is rendered harmless generally by a harm-removing agent using an iron oxide, an alkali metal compound or a alkaline earth metal compound, and an activated carbon or an activated carbon having supported thereon an effective components.
Among these, in the case of the harm-removing agent of (6), the harm-removing ability for chlorine, boron trichloride and the like is equal to, for example, that of activated carbon but the harm-removing ability for hydrogen halide, silicon fluoride and the like is higher. However, when halogen-containing gas in the dry etching exhaust gas is actually treated, the harm-removing ability decreases in many cases including the methods of (1) to (5) and the harm-removing agent must be frequently exchanged, as a result, the cost for the treatment of dry etching exhaust gas increases.
The main factor of causing the decreasing of the harm-removing ability is in the water washing of the etching chamber. More specifically, the washing of the etching chamber is very important to prevent the generation of particles due to the deposit produced during the etching or to prevent corrosion by the halogen-containing gas. In almost all of the methods for washing the chamber employed by the manufacturers of semiconductor device, water is used as the most effective washing agent. When the aluminum, tungsten silicide, silicon oxide film, gallium arsenide, indium phosphide, gallium phosphide or the like is etched using halogen-containing gas such as hydrogen halide, boron trichloride or chlorine gas, the etching gas and many halogen-containing gases produced during the etching contained in the exhaust gas react with the washing water as follows to produce hydrogen halide:
SiX4+4H2Oxe2x86x924HX+Si(OH)4, COX2+H2Oxe2x86x922HX+CO2
(X: F, Cl, Br)
BCl3+3H2Oxe2x86x923HCl+H3BO3, SF4+2H2Oxe2x86x924HF+SO2
In such a situation, the agent for rendering halogen-containing gas harmless in the dry etching exhaust gas must be, as a mandatory requirement, a harm-removing agent particularly having high harm-removing ability for hydrogen halide produced by the hydrolysis reaction. The harm-removing agent is also required to be effective for other halogen-containing gases. However, the techniques at present have not yet succeeded in providing an agent and a method capable of rendering halogen-containing gas harmless contained in the dry etching exhaust gas at the low cost while revealing high harm-removing ability (per unit volume), and the development thereof is demanded from many manufacturers of semiconductor device.
The present invention has been made under these circumstances and the object of the present invention is to provide an agent and a method for removing harmful gas, favored with high harm-removing ability per unit volume for halogen-containing gas contained in the etching or cleaning exhaust gas and also favored with inexpensiveness.
As a result of extensive investigations to solve the above-described problems, the present inventors have found that a harm-removing agent containing the specific iron oxide, an alkaline earth metal compound and activated carbon in the specific amount exhibits high harm-removing ability particularly for hydrogen halide and by this, the problems described above can be solved. The present invention has been accomplished based on this finding. The present invention provides an agent and a method for rendering halogen-containing gas harmless and a method for manufacturing a semiconductor device using them, as described in the following (1) to (22).
(1) A harm-removing agent for rendering halogen-containing gas harmless, comprising 10 to 40 wt % of an iron oxide selected from the group consisting of xcex3-iron oxide hydroxide and xcex3-ferric oxide, 20 to 80 wt % of an alkaline earth metal compound and 10 to 40 wt % of an activated carbon.
(2) The harm-removing agent for rendering halogen-containing gas harmless as described in (1) above, wherein said alkaline earth metal compound is at least one selected from the group consisting of oxides, hydroxides and carbonates of magnesium, calcium, strontium and barium.
(3) The harm-removing agent for rendering halogen-containing gas harmless as described in (1) or (2) above, wherein said activated carbon has a specific surface area of 500 m2/g and more.
(4) The harm-removing agent for rendering halogen-containing gas harmless as described in any one of (1) to (3) above, which contains calcium sulfate.
(5) The harm-removing agent for rendering halogen-containing gas harmless as described in (4) above, wherein the content of said calcium sulfate is from 0 to 0.2 per 1 mass in total of iron oxide, alkaline earth metal compound and activated carbon.
(6) The harm-removing agent for rendering halogen-containing gas harmless as described in any one of (1) to (5) above, which is a particulate product obtained by blending the iron oxide, the alkaline earth metal compound, activated carbon and calcium sulfate each in the form of powder having a particle size of 100 xcexcm or less, and granulating the blend.
(7) The harm-removing agent for rendering halogen-containing gas harmless as described in (6) above, which is a particulate product having a particle size of 0.5 to 10 mm.
(8) The harm-removing agent for rendering halogen-containing gas harmless as described in any one of (1) to (7) above, wherein said halogen-containing gas is at least one gas selected from the group consisting of halogen, hydrogen halide, silicon halide, tungsten halide, carbonyl halide, sulfur fluoride, arsenic chloride, phosphorus chloride, aluminum trichloride and boron trichloride.
(9) A harm-removing method for rendering halogen-containing gas harmless, comprising contacting a gas containing halogen-containing gas with the harm-removing agent described in any one of (1) to (8) above.
(10) The harm-removing method for rendering halogen-containing gas harmless as described in (9) above, wherein said halogen-containing gas is at least one gas selected from the group consisting of halogen, hydrogen halide, silicon halide, tungsten halide, carbonyl halide, sulfur fluoride, arsenic chloride, phosphorus chloride, aluminum trichloride and boron trichloride.
(11) A harm-removing method for rendering halogen-containing gas harmless, comprising a step of contacting a gas containing halogen-containing gas with a harm-removing agent comprising activated carbon and subsequently to said step, a step of contacting the gas with the harm-removing agent described in any one of (1) to (8) above.
(12) The harm-removing method for rendering halogen-containing gas harmless as described in (11) above, wherein said activated carbon has a specific surface area of 500 m2/g or more and a particle size of 0.5 to 10 mm.
(13) The harm-removing method for rendering halogen-containing gas harmless as described in (11) or (12) above, wherein said halogen-containing gas contains a halogen gas and further contains at least one gas selected from the group consisting of hydrogen halide, silicon halide, tungsten halide, carbonyl halide, sulfur fluoride, arsenic chloride, phosphorus chloride, aluminum trichloride and boron trichloride.
(14) A harm-removing method for rendering halogen-containing gas harmless comprising a step of contacting a gas containing halogen-containing gas with the harm-removing agent described in any one of (1) to (8) above, and subsequently to said step, a step of contacting the gas with a harm-removing agent comprising zeolite.
(15) The harm-removing method for rendering halogen-containing gas harmless as described in (14) above, wherein said zeolite is synthetic zeolite and/or natural zeolite and has a particle size of 0.5 to 10 mm.
(16) The harm-removing method for rendering halogen-containing gas harmless as described in (14) or (15) above, wherein said synthetic zeolite is MS-5A and/or MS-13X.
(17) The harm-removing method for rendering halogen-containing gas harmless as described in any one of (14) to (16) above, wherein said halogen-containing gas contains sulfur dioxide and further contains at least one gas selected from the group consisting of hydrogen halide, silicon halide, tungsten halide, carbonyl halide, sulfur fluoride, arsenic chloride, phosphorus chloride, aluminum trichloride and boron trichloride.
(18) The harm-removing method for rendering halogen-containing gas harmless as descriebed in any one of (9) to (17) above, wherein the halogen-containing gas concentration in said gas to be treated is 10 vol % or less.
(19) A method for manufacturing a semiconductor device, comprising an etching or cleaning step of using at least one gas selected from the group consisting of fluorocarbon, sulfur hexafluoride, halogen, hydrogen halide and boron trichloride as an etching or cleaning gas, and a harm-removing step of contacting a gas containing halogen-containing gas discharged from said etching or cleaning step with the harm-removing agent described in any one of (1) to (8) above to rendering the halogen-containing gas harmless.
(20) The method for manufacturing a semiconductor device as described in (19) above, wherein said harm-removing step contains a step of contacting the gas with a harm-removing agent comprising activated carbon.
(21) The method for manufacturing a semiconductor device as described in (19) above, wherein said harm-removing step contains a step of contacting the gas with a harm-removing agent comprising zeolite.
(22) The method for manufacturing a semiconductor device as described in any one of (19) to (21), wherein the halogen-containing gas concentration in the gas discharged from the etching or cleaning step is 10 vol % or less.